Pulsed oscillator of the magnetron type



March 14, 1950 P. L. SPENCER 2,500,328

PULSED OSCILLATOR OF THE MAGNETRON TYPE Filed March 27, 1945 lllll u l;um

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I mam rm Br e 4. Sff/VCi/fl Fatenied ar. 14, 195G UNITED STATES OFFIEPercy L. Spencer, West Newton, Mass, assignor to Raytheon ManufacturingCompany, Newton, Mass, a corporation of Delaware Application March 27,1945, Serial No. 585,024

Claims.

This invention relates to an electron discharge device of the magnetrontype and more particularly to such a device which is operated bysupplying pulses of voltage between the cathode and anode thereof so asintermittently or periodically to energize the device.

In devices of this kind the magnitude of the magnetic field ordinarilyis such as to require magnet structures of considerable size and weight.

An object of my invention is to devise such an arrangement in which themassive magnet structure heretofore required may be subtantiallyeliminated.

Th foregoing and other objects of this invention will be best understoodfrom the following description of an exemplification thereof, referencebeing had to the accompanying drawing wherein:

Fig. 1 is a diagrammatic view of an arrangement incorporating myinvention showing a magnetron tube in longitudinal cross section takenalong line |l of Fig. 2; and

Fig. 2 is a transverse cross section of the magnetron taken along line2-2 of Fig. 1.

lhe magnetron illustrated comprises a glass envelope I which is closedat on end by a reentrant stem 2 supporting an electrode structure. Thiselectrode structure consists of an anode 3 and a cathode t centrallydisposed therein. The cathode l may be of the thermionic filamentarytype coated with suitable emitting oxides.

The anode comprises a hollow box 5 made of suitable highly conductingmaterial such as copper. Fastened to the upper wall of said box andextending inwardly therefrom is a pair of anode plates 6. Between theanode plates 6 and on each side thereof is a corresponding pair of anodeplates I fastened to the lower Wall of said box 5 and extending inwardlytherefrom. It will be noted that a circuit is completed between eachadjacent pair of anode arms 6-! which extends through the walls of thebox 5. Each circuit thus defined contains capacity and inductance andconstitutes a cavity resonator so that when the device is operated so asto produce oscillations therein, the frequency of said oscillations isdetermined by the natural frequency of such cavity resonator.

The anode is electrically connected to and supstandards [0 and H. Thestandards 8, l0. and 55 I l are electrically connected to lead-in wiresl2, l3, and M which are sealed through the press 2 and extend to theexterior of the tube whereby electrical external connections may be madethereto.

When the device as described above is energized with proper voltage anda strong magnetic field is created transverse to the direction ofelectron fiow between the cathode 4 and the anode plates 6 and l, thedevice generates ultra-high frequency oscillations. These oscillationsmay be led out from the tube by a coupling loop l5 extending into thehollow box 5 in the proper position to be coupled to the magnetic vectorof the oscillations within said box. One end of the coupling loop US maybe electrically connected at E6 to the box 5. The other end of said loopmay pass through an opening H in the sid wall of said box 5. The ends l8and IQ of said loop l5 are sealed through the side wall of the envelopel and constitute a transmission line whereby the oscillations may be fedto asuitable consumption device.

In order to create the magnetic field necessary to produce the magnetronoperation, there is supported within the box 5 a coil 20 of highconducting, material capable of carrying large values of current. Oneend of said coil may be electrically connected to the box 5 as by beingwelded to the upper end of anode standard 8. The other end of the coil20 passes out from the hollow box 5 through an insulator 2| and isconnected to a conducting standard 22 sealed in the press 2. Thestandard 22 has connected thereto a lead-in conductor 22' sealed throughthe press 2 and extending xteriorly of the tube.

The filamentary cathode 4 may be supplied with heating current from atransformer 23 having a primary 24 connected to a suitable source ofalternating current and having a secondary 25 connected to the lead-inconductors l3 and i l.

As previously indicated the magnetron is to be operated so as to supplypulses of ultra-high frequency oscillations. For this purpose the deviceis supplied with pulses of power from a condenser 20 which is chargedfrom a suitable sourc of direct current 27 through a currentdimitingresistance 28. The negative end of the condenser 26 is connected bymeans of a conductor 20 to a center tap on the secondary winding 25. Thepositive side of condenser 26 is connected through a switch 30 to thelead-in conductor E2. The switch 30 may be periodically closed at anydesired repetition rate. This may be of the order of 1000 cycles persecond or more. Of course, it

is to be understood that switch 31) could be operated according to anyother desired time pattern.

Whenever the switch 3B closes, the anode 3 is made positive with respectto the cathode d. The time constant of the discharge circuit of thecondenser 25 is so small that the voltage is applied between the cathodeand anode substantially simultaneously with a very high dischargecurrent flow through the coil 2b which creates the necessary magneticfield. The combination of this magnetic held and the anode voltagecauses the device to generate a short pulse of oscillations. In pulseoperation of this type the duration of the pulse can be very short sothat it is a relatively simple matter to design th circuits in such away that both the anode voltage and the current flow exist for asufficient period to produce the desired length of pulse. Since thecurrent flows through the coil for only a very short period of time, forexample, of the order of several micro-seconds, an enormous value ofcurrent can be passed through said coil without in any way tending todamage any of th parts of the device. This value of current may bereadily made of such a value as to create a high intensity of magneticfield sufficient to produce the proper magnetron operation.

When the condenser hasbeen discharged the switch 33 is re-opened. Thetime constant of the charging circuit for the condenser 26 is designedso that said condenser is sufhciently charged to the proper voltagebefore the switch 38 re-closes.

Of course, it is to be understood that this invention is not limited tothe particular details as described above inasmuch as many equivalentswill suggest themselves to those skilled in the art. It is accordinglydesired that the appended claims be given a broad interpretationcommensurate With the scope of the invention within the art.

What is claimed is: v

1. A magnetron oscillator comprising a cathode, an anode adjacent saidcathode and spaced therefrom to provide a discharge path for the how ofelectrons from said cathode to said anode, a coil surrounding saiddischarge path with the axis of said coil substantiall transverse to thedirection of said flow of electrons, means, connected between saidcathode and anode, and across said coil, for substantiallysimultaneously supplying a pulse of voltage between said cathode andanode and a pulse of current through said coil. 7 I 4 2. A magnetronoscillator comprising a cathode, an anode adjacent said cathode andspaced therefrom to provide a discharge path for the flow of electronsfrom said cathode to said anode, a coil surrounding said discharge pathwith the axis of said coil substantially transverse to the direction ofsaid fiow of electrons, a condenser, means, connected across saidcondenser and between said cathode and anode, and establishing apotential difierenc'e between said cathode and anode, and means,connected between said condenser and said coil, for discharging saidcon- 4 denser through said coil and substantially simultaneouslyconnecting said first-named means between said cathode and anode.

3. A magnetron oscillator comprising a cathode, an anode adjacent saidcathode and spaced therefrom to provide a discharge path for the flow ofelectrons from said cathode to said anode, said anode comprising aplurality of anode arms, each pair of adjacent anode arms, together withthat portion of said anode lying therebetween, providing a, cavityresonator, a coil surrounding said anode arms with the axis of said coilsubstantially transverse to th direction of said flow of electrons,means, connected between said cathode and anode, and across said coil,for substantially simultaneously supplying a pulse of voltage betweensaid cathode and anode and a pulse of current through said coil.

4. A magnetron oscillator comprising a cathode, an anode adjacent saidcathode and spaced therefrom to provide a discharge path for the flow ofelectrons from said cathode to said anode, said anode comprising aplurality of anode arms, each pair of adjacent anode arms, together withthat portion of said anode lying therebetween, providing a cavityresonator, a coil surrounding said anode armswith the aids of said coilsubstantially transverse to the direction of said flow of electrons, acondenser, means, connected across said condenser and between saidcathode and anode, for charging said condenser, and establishing apotential difference between said cathode and anode, and means,connected between said condenser and said 0011, for dis;- charging saidcondenser through said coil and substantially simultaneously connectingsaid first-named means between said cathode and anode.

5. A magnetron oscillator comprising an anode structure including acylindrical body closed at its ends by end plates and havinginwardlyextending anode arms projecting alternating from said endplates, a cathode axially disposed Within said anode structure, acoildisposed within said anode structure surrounding said anode arms, andmeans, connected between said cathode and anode structure, and acrosssaid coil, for substantially simultaneously supplying a voltage pulsebetween said cathode and anode structure and a current pulse throughsaid coil.

PERCY L. SPENCER.

riEFERENoEs CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,500,328March 14, 1950 PERCY L. SPENCER It is hereby certified that errorsappear in the printed specification of the above numbered patentrequiring correction as follows:

Column 1, line 13, for subtantially read substantially; column 3, line64, after the Word and comma anode, and before and insert for chargingsaid condenser; column 4, line 31, after condenser strike out the comma;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Oflioe.

Signed and sealed this 4th day of July, A. D. 1950.

[SEAL] THOMAS F. MURPHY,

Assistant Commz'ssz'oner of Patents.

